Organosilanes which contain epoxy groups have for some years been attracting a great deal of technical interest. They are used, for example, as adhesives for the combination of certain organic polymers, such as epoxy resins or phenolic resins with glass fibers, fabrics or roving, and for improving adhesion in the bonding of sand molds. Successful attempts have already been made for the improvement of the adhesion between plastics and metals on the basis of the use of such silanes.
The synthesis of these epoxy organosilane esters has hitherto been possible through a variety of methods. For example, organosilane esters containing carbon double bonds are oxidized with peroxides to produce such epoxides. This method, however, is not generally applicable to the synthesis of the entire class of substances owing to poor compatibility with the sensitive silane esters. On the other hand, it suffers from by-products which necessarily arise from the peroxides and therefore it is economically unprofitable. Furthermore, the use on a large technical scale of the peroxides suitable for this procedure, such as peracetic acid, entails considerable safety risks.
Another known method of manufacturing epoxy organosilane esters is the catalytic addition of hydrogen silane esters onto the carbon double bond of a monolefinic epoxy compound. The catalysts used for this purpose are essentially simple or complex compounds of nickel, platinum, rhodium or ruthenium.
The disadvantage of this process lies especially in the action of the basic epoxy group on the base-sensitive hydrogen silane esters. This leads on the one hand to competing disproportionation reactions with the formation of higher silane esters and hydrogen silanes. On the other hand, this basicity is so great that it has a poisoning effect on the catalysts. Since in this process a satisfactory transformation is not achieved until temperatures of 130.degree.C and up are reached, these competing reactions may become very undesirably evident. In addition, the catalysts also bring about the hydrogenation of the olefinic center of addition. Numerous attempts have therefore been made to overcome these disadvantages by complex variants at the central atoms of the catalysts, and gradual improvements have indeed been achieved, although it has not been possible to completely eliminate the described difficulties.
Inasmuch as the catalytic addition of chlorosilanes rather than the sensitive hydrogen silane esters runs into difficulties on account of the basicity of the epoxy compounds, attempts have also been made to use hydrogen fluorosilanes as starting materials. The epoxy organofluorosilanes thus obtained then have to be reesterified.
This procedure again involves the disadvantage of the introduction of a two-stage process, while the known disadvantages of catalyst poisoning and of the competing hydrogenation reaction are not eliminated. In addition, working with hydrogen fluorosilanes requires the expensive safety measures and procedures which are necessarily involved in fluorine chemistry, so that higher first costs are involved in the application of this process.